1. Technical Field
The present disclosure relates to advantageous methods and apparatus for spinal stabilization. More particularly, the present disclosure relates to methods and apparatus for providing dynamic stabilization to the spine so as to provide clinically efficacious results and to such methods/apparatus that include travel-limiting functionality.
2. Background Art
Low back pain is one of the most expensive diseases afflicting industrialized societies. With the exception of the common cold, it accounts for more doctor visits than any other ailment. The spectrum of low back pain is wide, ranging from periods of intense disabling pain which resolve to varying degrees of chronic pain. The conservative treatments available for lower back pain include: cold packs, physical therapy, narcotics, steroids and chiropractic maneuvers. Once a patient has exhausted all conservative therapy, the surgical options generally range from micro discectomy, a relatively minor procedure to relieve pressure on the nerve root and spinal cord, to fusion, which takes away spinal motion at the level of pain.
Each year, over 200,000 patients undergo lumbar fusion surgery in the United States. While fusion is effective about seventy percent of the time, there are consequences even to these successful procedures, including a reduced range of motion and an increased load transfer to adjacent levels of the spine, which may accelerate degeneration at those levels. Further, a significant number of back-pain patients, estimated to exceed seven million in the U.S., simply endure chronic low-back pain, rather than risk procedures that may not be appropriate or effective in alleviating their symptoms.
New treatment modalities, collectively called motion preservation devices, are currently being developed to address these limitations. Some promising therapies are in the form of nucleus, disc or facet replacements. Other motion preservation devices provide dynamic internal stabilization of the injured and/or degenerated spine, e.g., the Dynesys stabilization system (Zimmer, Inc.; Warsaw, Ind.) and the Graf Ligament. A major goal of this concept is the stabilization of the spine to prevent pain while preserving near normal spinal function.
To provide dynamic internal spinal stabilization, motion preservation devices may advantageously include stabilizing members that exhibit multiple degrees of freedom and commonly include active force-absorbing/force-generating structures. Such structures may include one or more resilient elements, e.g., torsion springs and/or wire coil springs, designed and deployed so as to contribute strength and flexibility to the overall device. While the flexibility afforded by such resilient elements is plainly critical to the effectiveness of the respective devices of which they form a part, the elevated force levels associated with the use of such resilient elements can result in such resilient elements developing significant levels of internal stress and/or responding to such stress by undergoing significant deformation, either or both of which may be undesirable depending on the particular device or surgical application.
With the foregoing in mind, those skilled in the art will understand that a need exists for devices, systems and/or methods for motion-preserving spinal stabilization devices and systems having stabilizing members with resilient elements, the internal stress levels and deformation response characteristics of which are appropriately controlled and managed. These and other needs are satisfied by the devices, systems and methods disclosed herein.